CHEMICAL EMBRYOLOGY: TECHNOLOGIES FOR MANIPULATING AND VISUALIZING DEVELOPMENT Abstract The emergence of pattern during embryogenesis requires dynamic control of gene function with spatiotemporal precision. Genetic screens and transgenic models have revealed many of the molecular mechanisms that regulate this transformation, and the completion of multiple genome sequencing projects has provided a comprehensive list of developmental genes. Our efforts to understand embryonic patterning at the molecular and systems levels, however, have been limited by current technologies for studying embryological processes. New methods for controlling and visualizing gene function in vivo are needed. In this application we describe synthetic probes that will enable the detection of endogenous RNAs or tagged proteins in live organisms, with at least picomolar sensitivity. In particular, we will develop reagents that couple gene expression with lanthanide luminescence and utilize them to interrogate the molecular mechanisms of zebrafish embryogenesis. The proposed reagents build upon our expertise in synthetic chemistry and zebrafish embryology, and they complement reverse-genetic technologies previously developed by our laboratory. Using these chemical tools, developmental biologists will be able to simultaneously observe gene function and morphogenesis in real time, providing an unprecedented mechanistic view of embryogenesis.